Network switching system with asynchronous and isochronous interface

ABSTRACT

To provide a switching system with telephone switching function mainly on the basis of hardware processing by using isochronous channel which is a real time communication channel. The switching system comprises a gateway node connected with ISDN (Integrated Services Digital Network) and PSTN (Public Switched Telephone Network), and one or more extension nodes, and a serial bus such as IEEE 1394 bus. The gateway node transforms data rate of outside line into data rate of extension node, and the other way around, and secure a seamless communication channel. Concretely, the gateway node secures an isochronous channel, according to a request from the extension nodes or the outside line, and executes switching such as transfer or reservation. A resource manager holds a table for managing the gateway node and extension node.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a switching method and equipment,wherein a serial bus is connected with extension nodes havingasynchronous interfaces and isochronous interfaces for switching signalsbetween an outside line and extension lines and between the extensionlines

DESCRIPTION OF THE PRIOR ART

Conventionally, switching devices for home use are simple, because theyare provided merely with an analogue or digital voice switch. Recently,however, information devices such as personal computers are introducedinto the home, and digital broadcasting becomes popular. Therefore,there are growing needs for distributing image signal, data signal,voice and audio signal to an individual or to individualssimultaneously.

Therefore, asynchronous transfer mode (ATM) and local area network (LAN)such as Ethernet are improved for distributing time series data such asaudio-visual signal.

Further, IEEE 1398 (IEEE Std. 1394-1995 IEEE Standard for a HighPerformance Serial Bus) is known by its real time and high speedperformance, and plug-and-play capability. Therefore, IEEE 1394 can beused in a high speed network for multi-media signal into the home. IEEE1394 applied to the home telephone is exemplified in FIG. 15. As shownin FIG. 15, digital voice signal 601 loaded on IP packet (InternatProtocol packet) 603 is transmitted by asynchronous transfer of IEEE1394 toward a peron on the other end of the line. Voice signal 601 isrecovered by assembling IP packet 603. Such a telephone system asexplained above simply is called IP telephony defined by ITU-T 11323.

However, ATM costs much, and Ethernet architecture can not guarantee thereal time performance for a plurality of time series data streams.

On the other hand, home use switching equipment for voice, audio-videosignals must be of low cost. In addition, it must have completeplug-and-play capability, when appliances are newly installed.

Actually, the IP telephony on IEEE 1394 as well as the IP telephony onthe internet requires additional competent software, CPU, and hardware,such as codec for DSP (digital Signal Processing).

However, completely natural voice is hardly obtained in general by theIP telephony, because the time series data stream is processed byasynchronous system.

Further, in an advanced network, the plug-and-play capability isindispensable for automatic recognition of newly installed appliances.

Connection route is changed often or even stopped by a bus reset on IEEE1394 for plug-and-play. However, the communication should not beinterrupted by such a bas reset.

Furthermore, the communication quality should be maintained underfluctuations in data traffic.

Further, it is desirable to provide such an advanced network with API(Application Program Interface) compatible with various operatingsystems and protocols.

Further, each terminal can identify other terminals by their ID numbersunder the plug-and-play circumstance.

Furthermore, it is desirable to provide a telephone equipment with suchfunctions as master-slave communication, slave-slave communication,master-slave transfer, and slave-slave transfer.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a switching method andsystem, wherein the telephone switching in the isochronous andasynchronous channels of IEEE 1394 is executed mainly by hardware.

A network switching system of the present invention exchanges streamdata on a serial bus through a gateway between an outside line and anextension node, or between an extension node and the other extensionnode, wherein the extension node comprises:

control/memory unit for storing physical identifiers and telephonenumbers of the gateway node and extension nodes and for controlling thenetwork;

an asynchronous interface, for selecting the extension node andcontrolling a switching timing, connected with the control/memory unit;

a rate conversion unit for converting data rate of the stream data inthe network into that in the outside line, or the other way around; and

an isochronous interface, for transmitting and receiving the streamdata, connected with the rate conversion unit.

A gateway of the present invention comprises a first switching unit forcontrolling extension nodes connected with a serial bus for isochronoustransfer, and second switching unit for exchanging stream data betweenan outside line and the extension nodes, wherein:

the first switching unit comprises a bus manager connected with anaysnchronous interface and an isochronous interface; and

the second switching unit comprises a line manager connected with acodec and a control/memory unit,

wherein the line manager exchanges the stream data between the outsideline and the extension line, according to a request from the busmanager, and the bus manager manages a call-in to the extension node anda call-out from the extension node.

An information terminal of the present invention comprises a telephonefor transmitting and receiving telephone signal through a serial bus, aTV set for receiving TV signal through the serial bus, and a bus managerfor controlling the serial bus, wherein the bus manager comprises twopairs of an aysnchronous interface and an isochronous interface for thetelephone signal and the TV signal.

A gateway of the present invention comprises a telephone gate way and aTV gateway which are connected with a bus manager, wherein:

the telephone gateway transfers telephone signal from public switchedtelephone network to a serial bus, and the other way around;

the TV gateway receives TV signal from TV line, and transfer the TVsignal to the bus manager; and

the bus manager comprises two pairs of an asynchronous interface and anisochronous interface for transferring the telephone signal and the TVsignal,respectively.

A call-in signal processing method of the present invention for anetwork switching system using asynchronous and isochronous transfer,wherein stream data on a serial bus are exchanged through a gatewaybetween an outside line and an extension node, or between an extensionnode and the other extension node, which comprises the steps of:

selecting at the gateway which of an automatic transfer by numberdisplay, a global call-in, or a manual call-in on the basis of setupdata;

calling one or more extension nodes;

securing one or more isochronous channels on the basis of responses fromthe extension nodes;

making the extension nodes start talking;

sending simultaneously call status of a station of which call status ischanged, to all the extension node connected with the serial bus.

A call-out signal processing method of the present invention for anetwork switching system using asynchronous and isochronous transfer,wherein stream data on a serial bus are exchanged through a gatewaybetween an outside line and an extension node, or between an extensionnode and the other extension node, which comprises the steps of:

receiving at the gateway a call-out from the extension node;

confirming at the gateway a call status of call object;

securing an isochronous channel for transmission;

sending the call status to all the extension nodes;

securing an isochronous channel for reception;

making the call object start talking, while sending, to the extensionnode which has made the call-out, such a call status that indicates theobject does not respond, when the object does not respond;

releasing the isochronous channels for transmission and reception, whendetecting an on-hook of the extension node which has made the call-out;and

sending the call status to all the extension nodes.

In the above-explained present invention, any special hardware such asATM switch is not employed. The switching system of the presentinvention employs a high speed serial bus such as IEEE 1394 andsubscriber circuit for interfaces.

Therefore, according to the present invention, CPU memory remains small,because the present invention does not employ complex protocol such asIP (internet protocol).

CPU also remains small, because 64 Kbps PCM digital conversion means andthe conversion hardware from 64 Kbps to 98.304, 199.0608, and 393.216Mbps are employed.

Further, according to the present invention, voice is natural, becauseISOCH channel is employed.

Further, according to the present invention, 64 Kbit data can betransmitted from the extension node by using the conventional 64 KbitCODE, and the addresses are managed by a simple table by fixing thechannel assigned at the time of the call-in and call-out.

Further, the data are transferred continuously even during the busreset, by optimizing the buffer.

Further, various voice and image applications on various OSs andprotocols are compatible with API (Application Program Interface).

In conclusion, according to the present invention, all the functionssuch as automatic identification of terminal functions, master-slavecommunication, slave to slave communication, and master to slavetransfer can be implemented.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a block diagram of the switching system of the presentinvention.

FIG. 2 is an example of a table for managing a gateway node andextension nodes.

FIG. 3 is a block diagram of a hardware of the gateway node.

FIG. 4 is a block diagram of the gateway node connected with ISDN(Integrated Services Digital Network).

FIG. 5 is a block diagram of a hardware of the extension node.

FIG. 6 is an illustration of signal conversion between voice/ISDN andIEEE 1394.

FIG. 7 is an illustration of IEEE 1394 packet.

FIG. 8 is a block diagram of an extension node which transmits andreceives voice signal only.

FIG. 9 is a block diagram of the protocol stack for extension-extensioncommunication by voice only.

FIG. 10 is a block diagram of gateway node connected with PSTN (PublicSwitched Telephone Network).

FIG. 11 is a block diagram of an extension node for voice and visualsignal.

FIG. 12 is a block diagram of residential gateway provided with atelephone gateway and a TV gateway.

FIG. 13 is a flow chart of call-in process.

FIG. 14 is a flow chart of call-out process.

FIG. 15 is a block diagram of a conventional IP (Internet Protocol)telephony.

PREFERRED EMBODIMENT OF THE INVENTION

Modes of embodiment of the present invention are explained, referring tothe drawings.

A protocol stack of the exchange system is shown in FIG. 1. The exchangesystem of the present invention comprises gateway node 700 which isconnected with a network such as a analogue line and ISDN (IntegratedServices Digital Network), one or more extension nodes 201, and IEEE1391 bus 301.

Extension node 201 which includes a voice node and a non-voice node isconnected with the physical layer of bidirectional IEEE 1394 bus 301.Therefore, the number of extension nodes 201 are smaller than or equalto sixty-three, according to the IEEE 1394 protocol. Further, extensionnodes 201 are equal on IEEE 1394 bus 301. Extension node 201 has its ownprotocol according to its own function. Extension node 201 can exchangeinformation data and control data with another extension node 201 whichhas the identical protocol. Further, extension node 201 can recognize abus reset due to addition or deletion of terminal, or dissolution oftrouble.

Gateway 700 includes a rate conversion means for converting theoutside/extension data transfer rates in order to provide call channelsfor seamless communication between the outside line and extension line.Further, in response to requests from outside line or extension line,gateway 700 grasps network status, and secures network resource,particularly the isochronous (ISOCH) channel as call channel.Furthermore, gateway 700 switches lines for transferring or holdingunder requests from outside or extension lines.

The normal or long distance standard in IEEE 1394 are employed for IEEE1394 bus 301.

Communication channels by a various means such as ISDN S-IF, CATV, ADSL(Asymmetric Digital Subscriber Line) and ATM (Asynchronous TransferMode) are used for outside line 101 connected with gateway 700.

Resource manager 401 prepares a control table for controlling extensiontable 201 and gateway node 700. The control table is exemplified in FIG.2. Simplified exchange number as shown in FIG. 2 is a number fixed tothe physical layer.

IEEE 1394 node control as shown in FIG. 2 is executed every node ID(identifier) in such a manner that gateway node 700 and extension node201 can refer to the simplified exchange number and the node classthrough IEEE 1394 bus 301.

When a bus reset occurs, the node ID is changed, according to the TreeIdentify process and the Self Identify process. In this case, resourcemanager 401 rewrites the control table and notifies each extension node201 of that change.

Node class is classified by its function into voice class, gatewayclass, and dataless class. A relay, for example, belongs to the datalessclass. Further, an automatic recording function during absence in thevoice class is indicated by suffix. These classes are identified by anon-shown exchange setup program.

A hardware block diagram of gateway node 700 is shown in FIG. 3. IEEE1394 bus 301 is connected with physical layer device 701 which isfurther connected through link layer device 702 with both asynchronous(ASYNC) interface 703 and isochronous (ISOCH) interface 704. Both ASYNCinterface 703 and ISOCH interface 704 are connected through internal businterface 710 with memory 709 and CPU 708. Gateway node 700 as shown inFIG. 3 inputs and outputs outside line signal by using outside lineinterface such as S-IF to and from memory 709 and CPU 708. B-chindicated as 706A and ISDN layer 2/layer 3 indicated as 706B areexemplified in FIG. 3.

A block diagram of another gateway node 700 connected with ISDN is shownin FIG. 4, wherein outside line interface 705 includes two informationchannels indicated as B-ch and control channel indicated as D-ch. Buffer706C as shown in FIG. 4 buffers signals as much as two informationchannels indicated as B-ch.

Gateway node 700 as shown in FIG. 3 or 4 is provided with non-shownexchange setup program.

Concretely, CPU 708 as shown in FIG. 3 or 4 accepts setup registrationof reception mode and stores it in memory 709 beforehand. The setupregistration is sent to CPU 708 from extension node 201 through physicallayer 701, link layer 702, ASYNC interface 703, and internal interfacebus 702. Here, the reception mode is selected by using operation boardsuch as ten key and is stored in memory 709. The reception mode may be,for example, a mode for calling extension node 201 with or withoutlimiting call originators, a mode for recording the voices automaticallywith or without limiting call originators.

When there is a call-in from ISDN, gateway 700 as shown in FIG. 3 or 4detects the number of the call originator from D-ch through outside lineinterface 705, and inspects, by using CPU 708, whether the object nodeis busy, idle, or absent.

When the termination node or the object node is busy, CPU 708 waits foran end of call.

On the other hand, when the termination node is idle, CPU 708 controlsASYNC interface 703, secures a bidirectional ISOCH channel, and send thesecured channel number to extension node 201. Then, afterward, ISOCHinterface 704 is activated under the control by CPU 708, therebystarting talking through the secured channel.

Further, when the termination node is absent, CPU 708 controls similarlyASYNC interface 703, secures a bidirectional ISOCH channel, and send toextension node 201 the secured channel number, recording ready signal,and recording identifier. Here, the recording identifier may includes asimplified exchange number, time, and serial number, whereby extensionnode 201 can record automatically the voice through gateway 700 fromISDN.

A hardware block diagram of extension node 201 is shown in FIG. 5. IEEE1394 bus 301 is connected through physical layer device 211 and linklayer device 212 with both asynchronous (ASYNC) interface 213 andisochronous (ISOCH) interface 214. Both ASYNC interface 213 and ISOCHinterface 214 are connected through internal bus interface 220 withmemory 221 and CPU 222. Extension node 201 further comprises userterminal 215.

User terminal 215 further comprises user interface 215A including anoperation board and voice input/output apparatus such as a microphoneand a speaker, and voice memory 215B for automatic recording duringabsent time. User terminal 215 may comprises a display for receivingvisual signals.

The output/input signal from/to user interface 215A is inputted oroutputted to/from memory 221 and CPU 222 through CODEC 218, buffer 219,and internal bus interface 220. The output/input signal from/to theoperation board is inputted or outputted to/from memory 221 and CPU 222through terminal controller 216, code extraction unit 217, and internalbus interface 220. The output/input signal from/to user interface 215Bis inputted or outputted similarly.

Extension node 201 transmits and receives the control signal of codeextraction unit 217, executes media stream transform of data such asvoice data, controls the operation board in user interface 215A, anddrives the speaker. The voice data may be coded by CODEC 218 and is sentto buffer 219 every 8 kHz sampling.

When the automatic recording at absent time is executed, a headerincluding the recording identifier is received through code extractionunit 217, a media stream of voice data is transformed by CODEC 208.Finally, the voice and the originator number and time stamp in thereceived header are stored in voice memory 215A.

Next, the communication from an extension node 201 to the otherextension node 201or to the outside line is explained. In this case, CPU222 inspects, on the basis of call operation by the operation board inuser interface 215A, whether the termination node 201 or gateway 700 isbusy, idle, or absent.

When the termination node 201 or gateway 700 is idle or absent, CPU 222send a call request through ASYNC interface 213. In case of extension toextension communication, CPU 222 secures an ISOCH channel for a streamchannel immediately after sending the call request, and send the securedchannel number to the termination node 201. In case of extension tooutside communication, CPU 222 further send the outside line numberthrough gateway 700. Then, CPU 222 sends a call request to the outsideline through gateway 700. Then, CPU 222 secures an ISOCH channel for astream channel between extension node 201 and gateway 700.

Signal conversion from voice/ISDN signal in the extension node into IEEE1394 signal in the network is illustrated in FIG. 6. Analogue voicesignal is sampled at 8 kHz by CODEC 218, coded by μ-LAW, buffered bybuffer 219, and sent through CPU 222 to IEEE 1394 link layer. Voicesignal is received in the direction reverse to the above-explainedprocedure. It is desirable that buffer 219 has a capacity sufficientenough to output the voice signals collectively, even when IEEE 1394 busstops and resumes.

IEEE 1394 packet signals and distributions thereof are illustrated inFIG. 7. Time slots of 5 μsec 801 and 802 contains ISOCH channels811,821, 812, and 822. For, example, a first node is assigned to channel1 of which first and second time slots are time slots 811 and 812,respectively. Likewise, a second node is assigned to channel 2 of whichfirst and second time slots are time slots 821 and 822, respectively.Data allocated to these time slots are converted into analogue signal byCODEC 208, and outputted from a speaker of user terminal 215. The voicesignal inputted into a microphone is processed in the direction reverseto the above-mentioned procedure for the speaker output.

In the present invention, synchronous interface may be, for example, aninterface for isochronous (ISOCH) transfer.

A block diagram of an extension node 201 exclusively used for voicesignal is shown in FIG. 8.

IEEE 1394 bus 301 is connected with ASYNC interface 703 and ISOCHinterface 704 through physical layer device 701 and link layer device702.

ASYNC interface 703 connected with control/memory unit 730 selects achannel in the network and controls signal timings. Control/memory unit730 stores network status by using reference means such as a table ofphysical ID and telephone number. Display unit 720 and operation unit721 which are connected with control/memory unit 730. Display unit 720displays network status on the basis of data from control/memory unit,while operation unit 721 accepts telephone number input.

ISOCH interface 704 outputs voice at 100 to 400 MHz every 125 u sec, atreal time, without re-transmitting, even when some errors have occurred.The outputted voice signal is converted into 64 Kbps ISDN signal by rateconversion means 731, processed by μ LAW/CODEC 732, and outputted fromspeaker 734. Reversely, voice signal inputted into microphone 733 istransferred to μ LAW/CODEC 732.

Further, stream data processing means 723 connected with stream datainput means 722 connected with rate conversion means 731 data format ofthe voice signal and stores it in a non-shown memory.

A protocol stack of extension to extension communication is shown inFIG. 9. Here, the extension nodes are used exclusively for voice signal.

Bus managers 750 and 751 as switching equipments are mounted on ASYNCinterface 703 /ISOCH interface 704 on link layer 702 on physical layer701. Bus managers 750 and 751control voice interface, rate conversion,and call information

Concretely, bus managers 751 for client and 750 for server control byusing a common manner for the client and server microphone/speaker,operation board, 721, and display 721.

Particularly, CTI 724 (Computer Telephony Integration) of bus manager750 for server controls connection and operation of terminals such asuser terminal 215 as shown in FIG. 5, stores the control information,executes notification to all the terminals, and accepts calls/requestsfrom the terminals. Here, the control information stored in CTI 724includes a correspondence table between the physical IDs of IEEE 1394and actual telephone number of the terminals. CTI 724 resumescommunication line instantly, by reading out the correspondence table,when the bus is reset.

The intermission of communication caused by the bus reset due to Plugand Play is minimized, because CTI 724 always make each terminal rewriteevery change in the correspondence table so as to restore the connectionmerely by notifying the terminal of the change of the physical ID due tothe Plug and Play.

A block diagram of gateway 700 connected with PSTN (public switchedtelephone network) is shown in FIG. 10. IEEE 1394 interface includingbus manager manages connection with IEEE 1394 bus 301 and executes voiceprocessing, while ISDN/analogue outside line interface connects digitalvoice stream through API (application program interface) of bus managerwith S interface of ISDN (S-IF) or the analogue interface.

CPU 708 converts protocols for connecting IEEE 1394 bus 301 andS-IF/PSTN 302. Concretely, address conversion between IEEE 1394 bus IDand telephone number, data conversion between high speed data on IEEE1394 bus 301 and low speed data on PSTN 302.

Line manager 752 accepts call-out from the bus manager and call-in fromthe outside line. Line manager 752 connects the call-in with extensionnode 201. Conventional hardware/software are employed for lower layersL2 (761) and L3 (762), CODEC 763, and control/memory unit 764.

A block diagram of extension node 201 for telephone data and TV data isshown in FIG. 11. Operation board 726 controls telephone 725 and TV 731.All the data from operation board 726 is sent to gateway 700 through busmanager and ASYNC channel. For example, billing information for digitalTV is sent through ASYNC channel as telephone data.

A block diagram of gateway node 700 for telephone data and TV data isshown in FIG. 11. Telephone gateway 727 connects NCU (Network ControlUnit) with IEEE 1394 bus 301, while TV gateway 728 connects digital TVwith IEEE 1394 bus 301. Operational data for controlling terminals andserver are sent through ASYNC channel to IEEE 1394 bus 301. For example,the billing information for digital TV is one of the operational data oftelephone. Telephone gateway 727 and TV gateway 728 are included in CPU708 as shown in FIG. 3.

TV signal stream on IEEE 1394 bus 301 is outputted on non-shown TVdisplay through physical layer, link layer, ASYNC interface, ISOCHinterface, and TV-AVF/C (TV-Audio Visual signal controller).

TV-AV signal may be MPEG (Moving Picture Expert Group of ISO/IEC)picture, while TV hardware may include STB (set top box).

A flow chart of the call-in operation is shown in FIG. 13. A call-inaccepted by S-IF or PSTN interface 761 is received as a connectionrequest at step 901. The call-in from analogue line is detected at ringdetection at step 902. Then, at step 903, CPU 708 selects either one ofthe three modes; automatic transfer by ND (number display), globalcall-in for all the extension nodes, or manual call-in to an objectextension node.

In case of the automatic transfer by ND at step 904, an ISOCH channel isselected on the basis of ND number, prescribed numbers to betransferred, and extension data.

In case of the global call-in at step 906, call signals to all theterminals are sent through ASYNC interface 704.

In case of the manual transfer at step 908, a call signal is sent to aswitching node or prescribed terminal, on the basis of an instructionfrom operation board 721.

After selecting the mode, CPU 708 decides to connect the call-in withextension node 201, or to reply “busy” to the outside line, dependingupon the status signals periodically sent from all the extension nodes201.

When CPU 708 confirms a reply from extension node 201, CPU 708 securesISOCH channel for extension node 201 and ISOCH channel for the outsideline at step 914, thereby starting communication at step 915. ISOCHchannels are secured till the end of call.

Further, when the call status is changed in extension node 201, thestatus change is notified simultaneously and directly to all theextension nodes 201 with telephone terminals. Here, the call status is asignal indicating whether a node is busy or idle.

A flow chart of call-out from an extension to the other extension or anoutside line is shown in FIG. 14. Connection is requested by connectionrequest at step 950 and by inputting an object telephone number orobject ID at step 951. The object ID is an object extension number, oran object outside line number together with prescribed number forcalling out the outside line. When gateway node 700 accepts theconnection request, it confirms the call status at step 952. When theobject is idle, ISOCH channel for transmission is secured at step 953,and Ch-ID is secured at step 954. Further, the call status is sent toevery node at step 955. Likewise, ISOCH channel for reception is securedat step. 956, Ch-ID thereof is secured at step 957, and the call statusis sent to every node at step 958. Then, at step 959, the call-outsignal is sent to the object through ASYNC channel. When the objectreplies, communication is started through ISOCH channel. On the otherhand, when the object does not reply, call signal is sent repeatedly,and a call status indicating that the object does not reply is sent tothe node which requests the cal-out. When the call-out is endedsuccessfully at step 962, or when on-hook by the node which requests thecall-out is detected due to at step 965, ISOCH channel is released atstep 966, and call status is sent to every node.

As explained above, ISOCH channel is secured every call.

Every call transmits one packet of maximum 16 Bit voice data every cyclewithin 1 μsec of ISOCH transfer.

The hardware necessary for the exchange system of the present inventionincludes CODEC for voice signal and rate conversion device together withphysical layer device and link layer device.

The API in the present invention feed the high bit rate voice data onIEEE 1394 into the processing unit.

The terminals of the present invention store the latest status, becausethe status change in a terminal is immediately notified to all theterminals. Therefore, the latest status can be confirmed before busreset and call. Particularly, busy status of the object can be confirmedbefore the beginning of ISOCH transfer.

1-9. (canceled)
 10. A device comprising: one or more processors to:receive a request to establish a connection for transmitting voicesignals between a first extension node and a second extension node, atleast one of the first extension node or the second extension node beingconnected to the device via a serial bus, secure, based on the request,a bidirectional isochronous channel, and transmit informationidentifying the bidirectional isochronous channel to one of the firstextension node or the second extension node to enable the connection tobe established.
 11. The device of claim 10, where the one or moreprocessors are further to: determine that the connection is associatedwith a telephone number of the first extension node, convert thetelephone number to an identifier associated with the first extensionnode, and notify, via the serial bus, each of a plurality of otherextension nodes connected to the serial bus, of the establishedconnection between the first extension node and the second extensionnode using the identifier.
 12. The device of claim 10, where the one ormore processors are further to: determine an occurrence of a reset ofthe serial bus, determine a change to an identifier associated with theat least one of the first extension node or the second extension nodethat is caused by the occurrence of the reset of the serial bus,transmit, via the serial bus and to the at least one of the firstextension node or the second extension node, information identifying thechange to the identifier to prevent a transmission of the voice signalsfrom being interrupted.
 13. The device of claim 12, where the occurrenceof the bus reset is caused by a connection of a third extension node tothe serial bus.
 14. The device of claim 10, where the one or moreprocessors are further to: determine a change to an identifierassociated with the at least one of the first extension node or thesecond extension node, transmit, via the serial bus and to the at leastone of the first extension node or the second extension node,information identifying the change to the identifier to prevent atransmission of the voice signals from being interrupted.
 15. The deviceof claim 10, where the first extension node and the second extensionnode are connected to the serial bus, and where the one or moreprocessors are further to: determine a state of the first extension nodebased on receiving the request, update control information based on thedetermined state, and transmit, prior to the connection beingestablished, information identifying the updated control information tothe first extension node and the second extension node.
 16. The deviceof claim 10, where the one or more processors are further to: determinea termination of the connection, and release the bidirectionalisochronous channel based on the termination of the connection.
 17. Amethod comprising: receiving, by a network device, a request toestablish a connection for transmitting voice signals between a firstextension node and a second extension node, the first extension nodebeing connected to the network device via a serial bus; securing, by thenetwork device, a bidirectional isochronous channel based on therequest; and transmitting, by the network device, informationidentifying the bidirectional isochronous channel to the first extensionnode to enable the connection to be established.
 18. The method of claim17, further comprising: determining that the connection is associatedwith a telephone number of the first extension node; converting thetelephone number to an identifier associated with the first extensionnode; and notifying, via the serial bus, each of a plurality ofextension nodes connected to the serial bus, of the establishedconnection between the first extension node and the second extensionnode using the identifier, the plurality of extension nodes includingthe first extension node and the second extension node.
 19. The methodof claim 17, further comprising: determining an occurrence of a reset ofthe serial bus; determining a change to an identifier associated withthe first extension node, the change to the identifier being caused bythe occurrence of the reset of the serial bus; transmitting, via theserial bus and to the first extension node, information identifying thechange to the identifier to prevent an interruption of a transmission ofthe voice signals.
 20. The method of claim 19, where the occurrence ofthe bus reset is caused by a connection of a third extension node to theserial bus.
 21. The method of claim 17, further comprising: determininga change to an identifier associated with the first extension node, andtransmitting, via the serial bus and to the first extension node,information identifying the change to the identifier to prevent atransmission of the voice signals from being interrupted.
 22. The methodof claim 17, where the first extension node and the second extensionnode are connected to the serial bus, the method further comprisingdetermining a state of the first extension node based on receiving therequest; and transmitting, prior to the connection being established,information identifying the state of the first extension node to thefirst extension node and the second extension node.
 23. The method ofclaim 17, further comprising: determining a termination of theconnection; and releasing the bidirectional isochronous channel based onthe termination of the connection.
 24. A method comprising: determining,by a first device, a first device identifier for a second device and asecond device identifier, that is different from the first deviceidentifier, for a third device, the first device, the second device, andthe third device being connected via a bidirectional serial bus;determining, by the first device, a first bus identifier for the seconddevice and a second bus identifier, that is different from the first busidentifier, for the third device; establishing, by the first device andusing the bidirectional serial bus, a communication session between thesecond device and the third device; determining, by the first device andduring the communication session, an occurrence of a bus reset of thebidirectional serial bus; determining, by the first device and duringthe communication session, a change of at least one of the first deviceidentifier or the second device identifier resulting from the occurrenceof the bus reset; and notifying, by the first device and during thecommunication session, the second device and the third device of thechange of the at least one of the first device identifier or the seconddevice identifier to minimize an intermission of communication caused bythe occurrence of the bus reset.
 25. The method of claim 24, whereestablishing the communication session includes: securing, based on arequest to establish the communication session, a first isochronouschannel and a second isochronous channel; and establishing thecommunication session over the first isochronous channel and the secondisochronous channel.
 26. The method of claim 24, where establishing thecommunication session includes: receiving a request to establish thecommunication session from the second device, transmitting, based on therequest, a signal to the third device via an asynchronous channel, andestablishing the communication session via a pair of isochronouschannels based on receiving, from the third device, a response to thesignal.
 27. The method of claim 24, where the occurrence of the busreset results from a fourth device being connected to the bidirectionalserial bus during the communication session.
 28. The method of claim 27,where notifying the second device and the third device of the change ofthe at least one of the first device identifier or the second deviceidentifier includes: transmitting, to the second device and the thirddevice, information identifying a third device identifier and a thirdbus identifier, the third device identifier and the third bus identifierbeing associated with the fourth device.
 29. The method of claim 24,further comprising: determining a termination of the communicationsession; and releasing the first isochronous channel and the secondisochronous channel based on the termination of the communicationsession.